1. Field of the Invention
The present invention relates to a method of correcting the load and attitude angle of a head suspension that supports a magnetic head slider in a hard disk drive, a method of manufacturing such a head suspension, the head suspension itself, and a method of processing a thin plate. In particular, the present invention relates to a method of correcting a head suspension, capable of precisely correcting the load and attitude angle of the head suspension even if the correction is repeated a plurality of times, a method of manufacturing a head suspension with the use of the correcting method, the head suspension thus manufactured, and a thin plate processing method employing the correcting method.
2. Description of Related Art
The recording density of hard disk drives has drastically improved in recent years, and accordingly, a precision requirement for head suspensions for supporting magnetic heads in the hard disk drives is becoming severer. The head suspension is designed to apply a predetermined load onto a magnetic head attached thereto and allow the magnetic head aerodynamically rise by a predetermined distance from a disk in a hard disk drive when the disk is turned at high speed. The attitude of the magnetic head in the risen state is greatly influenced by the load, roll angle, and pitch angle of the head suspension, and therefore, the load, roll angle, and pitch angle of every head suspension must correctly be adjusted during manufacturing. In this specification, the roll and pitch angles of a head suspension will be referred to collectively as “attitude angle.”
Generally, the load and attitude angle of a head suspension are corrected by holding a load beam of the head suspension or an outrigger formed at a front end of a flexure of the head suspension and by mechanically displacing, bending, or twisting the load beam or the outrigger. Mechanically holding and correcting the outrigger needs a jig specifically adjusted to the shapes of the head suspension and outrigger and a long time to move the jig, hold the outrigger, and process the outrigger. Namely, correcting a head suspension generally involves many processes and a long time.
To cope with this, Japanese Unexamined Patent Application Publication No. 2000-339894 proposes a technique of irradiating a head suspension with a laser beam, to thermally deform the head suspension and thereby correct the load and attitude angle of the head suspension. The applicant of the present invention has proposed in Japanese Unexamined Patent Application Publication No. 2004-82161 a technique of defining an irradiation area on a head suspension and irradiating the irradiation area with a laser beam, to draw a pattern of predetermined length and shape with the laser beam in the irradiation area and thereby correct the load and attitude angle of the head suspension. This technique bends an objective part of the head suspension by drawing a specific irradiation pattern in the part with a laser beam, thereby precisely correcting the load and attitude angle of the head suspension.
The precision requirement for head suspensions is continuously increasing and there is a strong need of manufacturing uniform head suspensions. To meet the requirements and needs, a head suspension must sometimes be corrected a plurality of times until it attain a specified load and a specified attitude angle.
For example, a head suspension once or several times corrected and still out of an allowable error range must be corrected again. Even an accepted head suspension must be corrected again if it shows an error after it is assembled with a magnetic head into a head gimbal assembly. Further, there is a possibility that a magnetic head already assembled with a head suspension into a head gimbal assembly shows an error in a product test. In this case, the magnetic head must be removed from the head suspension and must be replaced with another and the head suspension must be again corrected before or after it is reassembled with the replaced magnetic head (Japanese Unexamined Patent Application Publication No. 2002-93092).
The inventor of the present invention has found that, when a head suspension is corrected a plurality of times with a laser beam in such a way that a succeeding correction traces a preceding correction, the head suspension will not accurately be corrected.
When a part of a head suspension is once irradiated with a laser beam, to correct the load and attitude angle of the head suspension, substantially no change will occur in the load and attitude angle of the head suspension when the same part is again irradiated with a laser beam. This is because correcting the load and attitude angle of a head suspension with a laser beam is based on a bend produced by a thermal stress difference between a surface of the head suspension irradiated with the laser beam and an opposite surface thereof not irradiated with the laser beam.
The part once heated with a laser beam will show little change in internal stress when irradiated with a laser beam second time. Any head suspension once corrected with a laser beam does not provide an intended bend when it is irradiated with a laser beam again. This is the reason why repetitive corrections conducted on a head suspension cause a correction error in the load and attitude angle of the head suspension.
There is, therefore, a requirement for a new technique capable of precisely correcting the load and attitude angle of a head suspension or a thin plate even if a correction process is repeated a plurality of times on the head suspension (or thin plate).